The invention relates to a disc brake for a commercial vehicle.
DE 10 2008 036 765 A1 and DE 10 2009 018 223 A1 each disclose a disc brake, in which a rotationally fixed actuating spindle of a brake plunger forms a nut part which is guided on a threaded spindle which can be rotated relative to it, the internal thread of the actuating spindle and the external thread of the threaded spindle forming a thread pairing.
In order to compensate for a wear-induced change of an air play, that is to say the spacing between the brake application-side brake pad and a vehicle-side brake disc, the threaded spindle is rotated with respect to the actuating spindle which is held in a rotationally fixed manner, by way of an adjusting device which is arranged in the brake caliper.
To this end, the adjusting device has a drive gear which is connected in a rotationally fixed and axially secured manner to a drive spindle of the adjusting device and which is operatively connected to an output gear which is held in a rotationally fixed manner on the threaded spindle.
In the case of said known disc brakes, in each case two brake plungers which are arranged in parallel and at a spacing from one another are provided. These brake plungers can be driven for air play compensation via the adjusting device which is arranged centrally, that is to say between the two brake plungers, in order to compensate for the air play. Each actuating spindle is assigned an output gear, which output gears are a constituent part of a gearwheel mechanism of the adjusting device.
DE 10 2012 012 818 A1 discloses a comparable disc brake which, however, has merely one centrally arranged brake plunger, the actuating spindle of which is configured as a threaded sleeve, with an internal thread which is in engagement with a threaded spindle which can be rotated with respect to it and on the output gear of which in turn the drive gear (held in an axially secured manner) of the adjusting device, which is arranged laterally with respect to it, acts.
In addition to the gearwheel mechanisms which are known from the cited prior art, another gear mechanism can also be used to transmit the rotation of the adjusting device to the brake plunger or brake plungers, for example a flexible drive.
In the case of a braking operation, that is to say upon actuation of the brake lever, the brake plunger is displaced axially in the direction of the brake pad, including the output gear which is held in a rotationally fixed manner on the threaded spindle and, as has been mentioned, is operatively connected to the drive gear of the adjuster which, however, is positioned in an axially fixed manner. That is to say, the drive gear and the output gear perform a relative movement with respect to one another in the axial direction. This leads, however, to a considerable mechanical loading, by way of which the service life of the brake system is impaired.
The invention is based on the object of developing a disc brake of the abovementioned type in such a way that its functionality is improved and the service life is increased.
This object is achieved by way of a disc brake for a vehicle, in particular for a commercial vehicle, comprising: a brake caliper which straddles a brake disc; a brake application device which is arranged in the brake caliper for pressing brake pads onto the brake disc; at least one brake plunger which can be displaced axially by the brake application device; an adjusting device which is positioned in the brake caliper and is operatively connected via a gear mechanism to the brake plunger in order to adjust it axially in order to compensate for a wear-induced change in an air play, wherein the gear mechanism has a drive gear which is held on the adjusting device in a rotationally fixed manner and an output gear which is held on the brake plunger in a rotationally fixed manner. The output gear which is connected to the brake plunger in a rotationally fixed manner and the drive gear of the adjusting device, which drive gear corresponds with said output gear, are arranged in a driver device which is held such that it can be displaced axially but cannot be rotated.
In accordance with the invention, the drive gear of the adjusting device is mounted namely in a rotationally fixed manner, but such that it can be displaced axially, to be precise both in the brake application direction, that is to say in the braking direction, and in the release direction.
The mechanical loads which have been suffered up to now are avoided by way of the invention, according to which a driver device is provided, by way of which the two gear mechanism wheels which are operatively connected are coupled to one another in such a way that the braking-induced axial movement of the brake plunger is transmitted to the drive gear of the adjusting device.
This naturally results in an increase in the service life of the disc brake overall, with considerably reduced operating costs as a consequence which result firstly from the repair of the disc brake, including its spare parts supply, and secondly from the downtime of the commercial vehicle during the repair work.
Moreover, the operating or functional reliability of the disc brake is also improved by way of the invention, since the adjusting device is then functionally reliable as it were over the entire service life of the brake pads, that is to say up to their wear-induced replacement.
The driver device can be of very different design in structural terms, it being essential that the gear mechanism wheels which are operatively connected to one another are connected to one another in such a way that they remain freely rotatable.
To this end, coupling members are provided which, according to one preferred embodiment of the invention, consist of two plates which are in parallel and at a spacing from one another, preferably consist of sheet metal, and between which the gear mechanism wheels, for example gearwheels, but likewise also chain sprockets, are positioned.
Here, said two plates are connected to one another and are held at a spacing by way of suitable means such as beads, spacer sleeves or the like, which spacing is designed substantially in accordance with the thickness of the gear mechanism wheels. It goes without saying that other refinements of the coupling members are also contemplated.
As has been mentioned, the invention can be realized both in a disc brake with merely one brake plunger and also in a disc brake with two brake plungers. The brake plunger is arranged centrally with a laterally positioned adjusting device in the case of the former, whereas, in the case of a disc brake with two brake plungers, the adjusting device is arranged between them.
Here, the gear mechanism wheels bear against the two plates, preferably indirectly, with the involvement of sliding rings, on which the gear mechanism wheels are supported and which consist of a material which has a low coefficient of friction in correspondence with the gear mechanism wheel.
The sliding rings can be embedded into the plates or into the gear mechanism wheels themselves. The sliding ring assumes the form of a torus, with the result that there is a small contact area with the component which can be rotated relative to it.
Otherwise, the driver device can be manufactured very inexpensively, since the plates which substantially form the driver device are configured as simple punched sheet metal parts, into which the abovementioned beads can be formed at the same time as spacer elements. The beads protrude into the intermediate space which is formed by way of the two plates which are arranged at a spacing from one another, and bear against one another in such a way that they can be connected to one another, for example, by way of welding.
The spacer sleeves which are mentioned as spacer elements are likewise simple and inexpensive to manufacture, in particular as pipe sections.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.